Most computing systems tend to include one or more graphics processors to execute graphics (or even general-purpose) instructions. To perform their tasks, graphics processors may include one or more pipelines. In graphics pipelines, stencil testing is conceptually a per-sample operation occurring before depth testing.
However, per-sample tests (such as stencil tests, depth tests, etc.) can use non-trivial amounts of bandwidth, and may limit the overall throughput due to the sheer number of tests that may be employed.